Answer:
The Missouri Compromise of 1820 established the latitude 36°30′ as the northern limit for slavery to be legal in the territories of the west. As part of this compromise, Maine (formerly a part of Massachusetts) was admitted as a free state.
Step-by-step explanation:
This parallel of latitude is particularly significant in the history of the United States as the line of the Missouri Compromise, which was used to divide the prospective slave and free states west of the Mississippi River, with the exception of Missouri, which is mostly north of this parallel.